Etching machine



Oct. 31, 1939. PFAFFMANN 2,177,877

ETCH'ING MACHINE Filed Nov. 16, 1936 2 Sheets-Sheet l IN VENTOR,

J6 By 1%?! 'y 177159276017.

Patented Oct. 31, 1939 PATENT orriee ETCHING MACHINE Harry G. Pfafimann,Kansas City, Mo., assignor to Burger-Baird Engraving Company, acorporation of Missouri Application November 16, 1936, Serial No.111,089

6 Claims.

This invention relates to "electrical etching machines and has for oneof its, primary objects, the provision of means for more evenly anduniiormly etching printing platesv of relatively large areas through theuse of a main and supplemental grid forming the cathode in the machinewhile the piate being etched constitutes the anode.

a Oneoi the important aims of this invention is the provision in anelectricaletching machine of the aforementioned character, of asupplemental cathode which is supplied in addition to'the main cathodeof the apparatus, and in such relation thereto and to the plate beingetched as to produce highly desirable and unexpected results withoutcomplicating the machine nor adding to the cost of operation.

A number of minor objects will appear during the course of the followingspecification, referring to the accompanying drawings, wherein:

Figure 1 is a front elevation of an electrical etching machine made inaccordance with the present invention. I

Fig. 2 is a top plan View of the same.

Fig. 3 is a vertical, sectional View through the machine, taken on lineIII'III of Fig. 1.

Fig. 4 is an enlarged, detailed, longitudinal section through one of theplate, holders of the machine, and, v

Fig. 5 is a diagrammatical viewillustrating the electrical relationbetween. the anode and cathodes of the machine.

Referring to the drawingsillustratingthe preferred embodiment of theinvention, the numeral fidesignates a vat or like container for the bath8. This bath 8 may be ofthe conventional, well known character, but inpracticing the invention, it has been found thatv a saturated solutionof ordinary salt (NaCl) is satisfactory.

This bath, sometimes called an electrolytic bath,

m is a conductor and serves to submerge the hereinafter described anodeand cathodes. Vat 6, supported by legs or standards in, is provided withan outwardly extending shelf 12, upon which is mounted a motor I LhaVinga worm l6 secured M to its shaft. Pinion 18, in mesh with worm l6,

50 i8, eccentric to its axis of rotation. I

One end of rocker arm 20 carries a pintle' 28 that is journalled inbearings 30 mounted upon shelf l2. The other end of rocker arm 20 isbifurcated and the opposing jaws formed by the 55 bifurcation-areprovided respectively with slots 32, wherein rides cross pin 34,traversing yoke 36. Yoke 3% is substantially Y-shaped and the legthereof is in connection with the upper end of rocker arm'iifl throughthe medium of the aforesaid cross pin 34. The two legs of yoke 36 aresecured to the movable rack 38. This rack is substantially U-shaped andcomprises legs in, conheated by a number of slats 42, upon which restsasupplemental grid M. Rack 3a is mounted for movement through theemployment of tracks it, .1 one of which is mounted along the top of vat6, adjacent each end thereof, and guide bars 43,

that are maintained in parallelism with each track respectively bybrackets 58. Rollers $2, mounted upon legs til, ride along tracks 3B soas 15 to impart rectilinear reciprocating movement to rack 38 as motor Mdrives the aforementioned intermediate mechanism during the etchingoperation.

Main grid 56 is large enough to underlie grid 20 44 and plate 62 duringthe entire rectilinear reciprocating movement of grid and plate i i and62 respectively.

Spacer blockst l in the bottom of vat ii, support main grid 56 in spacedrelation to the floor of vat ii and below slats i2. A bus bar 558 restsupon the upper edges of legs it and carries two or more fixtures Ellthat support plate 82 to be etched. These fixtures are specially formedand shown in detail in Fig. 4. The body thereof is preferablybreated of.non-conducting material and has a longitudinal bore G l extendinginwardly from a notch 65 that is formed adjacent one end of the body. Astrap 88, having a hook it formed at the outer end thereof,longitudinally 35 traverses thebody of fixture 6E and terminates at aninturned foot 712 within notch 86. This foot 12 is faced as at i l witha silver coating so that plate 62 might contact the same.

To hold plate 82 against face "Hi, there is provided a plunger 16 ofnon-conducting material that is extended outwardly at one end in theform of a threaded shaft 18. A coil spring at urges plunger Hi againstplate 62 and turning thumb nut 82 will overcome the force of spring titand 45 withdraw plunger it from engagement with plate 62 when it isdesired to remove the plate from the fixture. Usually two of fixtures6|] are provided and mounted upon bus bar 58, as shown in Figs.

1 and 2. i

These fixtures 68 should be formed to hold plate 62 in spaced, parallelrelation with supplemental grid 44, and this last mentioned grid has anarea .much smaller than the area of main grid 56.

Sincesupplemental grid 44 is carried by rack 38,

it will be stationary with respect to plate 62 that is also carried byrack 38 and both 44 and 62 will be movable with respect to main grid 56in relatively spaced paths and in paths spaced from and parallel to maingrid 56.

In all instances, grid 44 and plate 62 have their centers on a commonline or in alignment vertically and grid 56 is large enough to alwaysextend beyond the edges of grid 44 and plate 62 during the etchingoperation so that the center of the plate being etched will be etched asdeeply as the marginal portions thereof. Thus one of the mosttroublesome shortcomings of electrical etching machines is overcome.

Reference to Fig. 5 will teach the manner in which plate 62, forming theanode, and grids 44 and 56, forming the cathode, are joined to aconventional source of current 84. This source of current may be agenerator of commercial type, and plate 62 is connected to the positivepole thereof by wire 86 and straps 68 of fixture 60. The cathodes in theform of grids 44 and 56, are joined to the negative pole of generator 84by a wire 88, so that the circuit is completed to eifectivelyelectrically etch plate 62.

It is conceivable that machines having widely varying characteristicsmight be made to embody this invention, and while the preferred form hasbeen illustrated and described, it is desired to be limited only by thespirit of the invention and scope of the appended claims.

Operation When plate 62 is in operative position in fixtures 60 with itsface side down and in a horizontal plane, motor I4 is started andcurrent for generator 84 directed through the circuit above traced. Grid44 and slats 42 of rack 38 will agitate the electrolytic bath betweenmain grid 56 and plate 62 sufficiently to wash the face of plate 62 andkeep the same clear of deposits and bubbles.

Main grid 56 is always large enough to underlie grid 44 and plate 62 andthe throw of link 22 and arm 2!] may be altered as desired.

Having thus described the invention, what is claimed as new and desiredto be secured by Letters Patent is:

1. An electrical etching machine comprising an electrolytic bath; meansfor supporting a plate therein to be etched; mechanism for moving saidsupporting means through a path of travel; conductors connecting theplate, which forms an anode, with the positive pole of a source ofcurrent; a main grid having an area appreciably greater than the platein spaced parallel relation with said plate; a supplemental grid,shorter in length than the anode plate, carried by the plate supportingmeans, between the said plate and said main grid for movement with theplate; and conductors connecting the main grid and the supplementalgrid, forming cathodes, to a source of current said main grid beinggreat enough in area to have a portion thereof in opposed relation tothe plate and supplemental grid as the same are carried by thesupporting means as it moves through said path of travel.

2. An electrical etching machine comprising an electrolytic bath; meansfor supporting a plate therein to be etched; mechanism for reciprocatingsaid supporting means; conductors connecting the plate, which forms ananode, with the positive pole of a source of current; a stationary maingrid in spaced parallel relation with said plate; a supplemental grid,shorter in length than the anode plate, carried by the plate supportingmeans, between the said plate and said main grid for movement with theplate; and conductors connecting the main grid and the supplementalgrid, forming cathodes, with the positive pole of the source of current,said supplemental grid being in spaced parallel relation with both themain grid and said plate said plate and the grids being in horizontalplanes, said main grid being lowermost and having an area great enoughto have a portion thereof below the plate and supplemental grid as thesame are reciprocated by the supporting means.

3. An electrical etching machine comprising an electrolytic bath; meansfor supporting a plate in a horizontal plane therein to be etched;mechanism for reciprocating said supporting means; conductors connectingthe plate, which forms an anode, with the positive pole of a source ofcurrent; a stationary main grid in spaced parallel relation with saidplate; a supplemental grid, shorter in length than the anode platecarried by the plate supporting means, between the said plate and saidmain grid, for movement with the plate; and conductors connecting themain grid and the supplemental grid, forming cathodes, with the positivepole of the source of current, said main grid, being below the saidplate in a horizontal position, said supplemental grid being spaced fromand parallel to both the main grid and said plate for the purposespecified the main grid being extensive enough in area to underlie theplate and supplemental grid as the same are reciprocated.

4. In an electrical etching machine having an electrolytic bath, a platetherein to be etched forming an anode, and a main grid forming acathode, the combination of a supplemental grid, shorter in length thanthe anode plate, forming a part of the cathode disposed between the maingrid and theplate having an area appreciably less than the area of themain grid and having its center in alignment with the center of theplate, said supplemental grid and the plate being mounted for movementthrough the bath in paths spaced from and substantially parallel to themain grid, said plate and the supplemental grid being in spaced parallelrelation to each other the area of said main grid being great enough tohave a portion thereof opposite the plate and supplemental gridthroughout their paths of travel.

5. In an electrical etching machine having an electrolytic bath, a platetherein to be etched forming an anode, and a main grid forming acathode, the combination of a supplemental grid, shorter in length thanthe anode plate, forming a part of the cathode disposed between the maingrid and the plate, said main grid having an area appreciably greaterthan the area of the plate and extending beyond the edges thereof,

6. An electrical etching machine having an electrolytic bath, a platetherein to be etched forming an anode, and a main grid forming acathode, the combination of a supplemental grid, shorter in length thanthe anode plate, formingv a part of the cathode disposed between themain grid and the plate having an area appreciably less than the area ofthe main grid and having its center in alignment with the center of theplate, said supplemental grid and the plate being mounted for movementthrough the bath in paths spaced from, substantially parallel with andin opposed relation to the main grid.

HARRY G. PFAFFMANN.

